A Quarter of a Century Against the Clock

A quarter of a century against the clock

25th anniversary time. Derek Lowenstein (left), chairman of Brookhaven's Alternat ing Gradient Synchrotron (AGS) Depart ment, presents a backwards-running clock to Ernest Courant, one of the pioneers of the AGS, which produced its first counter clockwise protons 25 years ago.

Twenty-five years ago, on 17 May 1960, the gleaming new Alternat ing Gradient Synchrotron (AGS) at the Brookhaven National Labo ratory, New York, got its first taste of protons. But it took a few more months to prepare the radiofrequency system which transformed the new ring from a toy into the most powerful particle accelerator in the world. On 29 July 1960, protons were whipped through the dreaded phase transition and accelerated to the 30 GeV design energy. The AGS had wrested the high energy crown from CERN's new Proton Synchrotron, which had achieved 24 GeV just five months previously. The AGS was the first proton accelerator project to incorporate from the start the revolutionary idea of strong focusing. In 1952, Brookhaven's Cosmotron, an old- style weak focusing machine, had supplied its first 3 GeV protons - the first time the 1 GeV barrier ward, some outward. in the American Library in Athens. had been breached. The same The initial idea was just to get On a trip to the US in 1952, he year, a group of European ma easier access to positive beams, saw the classic strong focusing chine specialists (Edouard Regen- but soon bigger payoffs became paper by Courant, Livingston and streif, Frank Goward, Odd Dahl evident. Collaborator Ernest Cour Snyder, and went along to Brook and Rolf Wideroe) from the infant ant found that rather than damag haven to tell them he had done it CERN came out to see what was ing the proton orbits, the new all before. John Blewett (also part happening. They were toying with idea seemed to improve the fo of Livingston's study group) the idea of building a scaled-up cusing. Hartland Snyder recog writes 'at first we thought he was version of the Cosmotron as the nized an analogy with optics, a phony but gradually facts first big machine for their new where alternate focusing and de- emerged to support his claim. We Laboratory. focusing lenses of equal strengths changed our minds and offered Cyclotron pioneer Stan Livings are focusing, no matter which him a job, which he accepted.' ton organized a study group to comes first. With the stronger fo The CERN team, which had un consider what advice Brookhaven cusing, magnet apertures could wittingly breathed hard enough could give the Europeans. During be cut from the 8 x 24 inches of down Brookhaven's neck to make the deliberations, Livingston had the Cosmotron down to matchbox Livingston and Co. come out with a brainwave. The Cosmotron size. something special, hurriedly magnets all faced outwards, mak (Unknown to the Brookhaven changed the design of their new ing it easy to extract negatively team, this idea had already been machine in midstream. At Brook charged particles from a target in developed by a Greek lift engineer haven, Leland Haworth persuaded the machine, but not positive called Nick Christofilos whose the US Atomic Energy Commis ones. Livingston's idea was to hobby was particle accelerators sion, very concerned with secret have some magnets facing in and who read the Physical Review work in those days, to let Brook-

234 CERN Courier, July/August 1985 haven publish the new ideas, and tery of CP-violation - the cunning J/psi particle and opened the door a modest six-page letter proposed way the neutral kaons break the to charm and more new physics. the building of the machine which rules of conventional physics. In (The J/psi was simultaneously was to become the AGS. (At Cor the same year, an AGS experi discovered by Burt Richter at nell, the strong focusing tech ment led by Nick Sarpios spotted Stanford.) nique was immediately the omega-minus particle, and a Against this impressive list of incorporated into a new electron new way of looking at physics achievements, the CERN PS had synchrotron which began opera suddenly clicked into place. only one of sipnilar stature - the tions in 1954.) The CERN team, Thanks to these and other dis sighting in 1973 of the neutral lender the direction of the late coveries in the 1960s, Brookhaven current of the weak interaction. Vohn Adams, went on to get their took over from Berkeley as the But by then the PS had embarked proton act together faster than world's premier particle physics on a new career, supplying pro Brookhaven. Laboratory. As if to confirm that tons to the big SPS machine built After the suspense of the con the initial bumper crop of results alongside. struction race, the AGS and the was no flash in the pan, a 1974 Towards the end of the 1970s, CERN PS machine embarked on experiment led by Sam Ting at a ambitious plans were again being their separate careers. There the more mature AGS discovered the formulated at Brookhaven and story was different. At the AGS in Pioneers of the AGS Brookhaven CERN. At Brookhaven, the AGS 1962, a team led by Mel Schwartz, Alternating Gradient Synchrotron alongside would feed the big ISABELLE pro an early scale model which showed the Leon Lederman and Jack Stein- great reduction in AGS magnet aperture ton-proton collider. At CERN, the berger discovered that there were compared to that of the Brookhavep SPS was already operating with Cosmotron thanks to the invention of the two types of neutrino. In 1963, alternating gradient focusing system. From particles from the PS. The plan James Cronin and Val Fitch made left to right are a youthful Ernest Courant, was to adapt the SPS to work as a Stanley Livingston, Hartland Snyder and the AGS beams reveal the mys John Blewett. proton-antiproton collider as well as a proton accelerator. While IS ABELLE foundered, the CERN project went from success to suc cess, achieving in its first years of operation the heady achievements which had been the privilege of the AGS physicists in the early sixties. However the spirit of the AGS physics teams remains indomita ble. After 25 years, the machine's physics potential is far from ex hausted, and a whole list of im provements is being pushed (see next story).

Plans for the future

Brookhaven is committed to the continuation of its robust high en ergy physics programme and to the initiation of a comprehensive fixed target and colliding beam programme for high energy (rela- tivistic) heavy ions. These initia-

CERN Courier, July/August 1985 235 tives result from the work of the and detector upgrades. BELLE project. As well as building AGS II Task Force (see June 1984 The other string to Brookha the RHIC itself, the AGS would issue, page 194) and other com ven's bow is heavy ions. Last have to be adapted for its new mittees. year, work got underway to allow role as the RHIC injector. The immediate particle physics heavy ions to be transferred from However the particle physics plans centre on improvements to the 16 MV tandem Van de Graaff content of the AGS programme is the 25-year old AGS - raising pro to the AGS (see December 1984 seen as continuing 'far beyond' ton beam intensities up to 5 x issue, page 433). As well as the the planned advent of the RHIC. 1013 particles per pulse, reliabili new transfer beamline, this re The AGS is tKe world's richest ties from 75 to 95 per cent, and quires modifications to existing source of kaons, and a pro beam duty factors from 25 to 45 beamlines and detectors, as well gramme of kaon physics would per cent; building a new booster as to the AGS itself. Ten weeks of include looking for rare decays to injector; improving beamlines and heavy ion running per year are fo test current ideas. Investigations detectors, and capitalizing on the reseen. of CP (charge conjugation/parity) spin physics capabilities which Subsequently, the new AGS violation, seen only in the neutral opened last year (see October booster could be adapted for kaon system, are vital if this long 1984 issue, page 328). heavy ion work, while further standing physics mystery is to be After this, a stretcher ring is en modifications could allow a wider finally understood. visaged to increase duty factors to range of heavy ions (up to atomic Other AGS particle physics ob 90 per cent or more, and power mass 200) to be handled. jectives include the neutrino sec supply and radiofrequency im For the 1990s, the big Relativis tor, where question marks still provements to push intensities up ts Heavy Ion Collider (RHIC) could loom as large as ever, spectros towards 1014 protons per pulse, be constructed in the tunnel origi copy in the 1 - 3 GeV region, together with further beamline nally made for the defunct ISA- where important new information could yet be obtained, and the study of hypernuclei (nuclei with one or more nucleons replaced by heavier particles) to provide an additional lever on particle inter actions. With polarized beams available in the AGS, the whole gamut of spin physics opens up. In addition, a new muon storage ring could be built to make even more precise measurements of the anomalous magnetic moment of the muon (see September 1984 issue, page 274).

Well-wishers crowd the experimental area at the AGS 25th anniversary party. (Photos Brookhaven)

236 CERN Courier, July/August 1985